This invention relates to a semiconductor device capable of integrating a bipolar transistor without requiring any special element isolation region and a method for manufacturing the same.
In a conventional bipolar integrated circuit, elements are electrically separated from one another by what is called a pn junction isolation method employing impurity diffusion. As these elements become finer to provide higher packing density, the area covered by element isolation regions becomes less negligible, giving rise to a substantial hindrance to the improvement in the packing density and further to the high-speed operation of the circuit. Moreover, in a conventional bipolar transistor of planar construction, a base region is embedded in a collector region, so that an unnecessary base-collector junction area is large. Further, despite a high-concentration embedded layer at the bottom of the collector region, the collector resistance is large enough to hinder the high-speed operation because a collector electrode terminal is taken out though the surface of the substrate.